The present disclosure is directed to a magnetic drain plug, and especially one which is installed in the oil pan of a automotive engine equipped with a crank case. The crank case is normally filled with lubricating oil. Lubricating oil is provided to lubricate the high speed operation of the crank shaft and piston rods which connect with it. In very general terms, substantial friction is created in this area The friction is reduced by filling the crank case with lubricating oil. In turn, the lubricating oil protects the rotating equipment.
There is the risk of metal particles being formed by the equipment. Abrasion and friction form particles which collect in the crank case. These particles can be cycled with the oil time and time again through the bearings and thereby damage the bearings. It is known to remove the particles with a filter. Sometimes, the flow lines in the crank case area do not direct all the oil through the filter. Rather, the metal particles fall out and collect in the oil pan thereby creating damages. Damage commonly is noted in the cylinder walls and seal rings. U.S. Pat. Nos. 5,465,078 and also 5,634,755 are pertinent to this inquiry. The '078 patent shows a magnetic drain bolt. It includes a bolt body with a magnet. This is one approach to collecting the small metal particles. Another device is the '755 patent just mentioned. It shows a bolt body with a magnet placed in it. Both of these represent devices which have met with measured success. There are limitations to them. Among the limitations, there is the spreading of the magnetic flux lines. In general terms, for a magnet of a specified or given strength, the magnetic flux lines extend outwardly from the magnet. The distribution of these flux lines in the immediate region is determined in part by the nature of the metals which support the magnet. The magnet in the references is held by a separable bolt. There is no recognition in the two references that the flux lines need to be dealt with least wide area distribution of the flux lines creates an effective magnet which is wider in size but which is reduced in intensity. The size of the magnet is enhanced as the flux lines are spread in the immediate region. In part, this depends on the magnetic response of the metal used to fabricate the bolt. In general terms, if a ferrous metal is used, it is relatively easily magnetized. The response of ferrous metal used in the bolt body and the construction of the oil pan causes a wider distribution of the magnetic flux. That however is not an advantage as will be noted below.
The flow velocity at the point of installation in the crank case may dislodge magnetically attracted particles. They will be dislodged by the high speed of the flow. Moreover they will be held in a wider region adjacent to the prior art devices just mentioned. Specifically some particles may be drawn to the bolt head and others to the magnet. However, some magnetic particles may fall through an eddy in the flowing oil and settle out, held magnetically next to the removable drain plug. Particles held magnetically to the oil pan are hard to remove. Periodically the engine lubricating oil is drained. This done by removing the plug. The metal particles on the plug can be wiped from the plug thereby removing them from the crank case. In the instance where fluid flow velocities are great in the crank case, the particles may be knocked loose from the bolt head, flushed around the crank case, and ultimately dropped out by eddy velocities and will be held by the magnetized region of the oil pan. When the bolt is removed and cleaned, some but not all of the particles will be removed. This is clearly the inference in the '078 patent as shown in the drawings and is tacitly the net result accomplished also in the '755 structure noting FIG. 8 thereof.
The apparatus of the present disclosure provides a magnet which is held higher in the region of oil flow. It is exposed to the oil flowing above the oil pan. It is also exposed to the oil at a higher elevation in the crank case. This location has an advantage and a comparable disadvantage. One advantage is that the magnet is exposed to substantially all the oil in the crank case because it flows by with significant scavenging velocity to thereby pick up particles and circulate them in near proximity to the magnet. This increases the likelihood that a metal particle will pass by and thereby be held by the magnet. In this region there is less likelihood that particles flowing by will be caught on the magnetism otherwise found in the distributed areas of the oil pan near the drain plug. This arrangement enhances the scavenging of this approach. It is accomplished however at a cost, namely, that it is closer to the rotating equipment and the flow velocities in the lubricant are more universal. With greater velocities, the likelihood of sweeping off previously collected particles increases. To counter this, the magnet of the present invention has a greater magnetic force. The force of the magnet is normally measured in units of strength known as oersteds.
It has been determined that the magnetic strength is optimum using a magnet sold under the Model TRI-NEO 30. This is a rare earth material magnet provided by Tridus International. It is made of a mixture of neodymium-iron boron. Other rare earth permanent magnets of comparable strength are acceptable. At temperatures common to those encountered in a crank case, this rare earth magnet provides permanent magnetic attraction which is better than ceramic or alnico (aluminum, nickel and cobalt) magnets. This is a sintered material which is shaped into an appropriate form. In this particular instance the form is preferably an elongate cylinder. Roughly, the sintered form of the magnetic material (generally the rare earth magnets) has very good magnetic strength at temperatures above about 100.degree. C. and are therefore quite acceptable in this environment. Even where the crank case temperature is maintained higher, it is not normally raised much above 120.degree. C. because excessive temperatures damage lubricating oils. Moreover, operation in the lubrication oil prevents corrosion on the surface. In that sense, corrosion and surface damage to the magnet is reduced or even prevented. In general terms it is able to provide about four to six times the energy product of the above mentioned alnico magnets. In general terms the alnico magnets define the standard; the rare earth magnets of this disclosure will operate at the appropriate temperatures and conditions.
The present disclosure is summarized as a three part system. The visible part is the removable crank case plug. The preferred materials are ceramics or metals which have minimal ferrous content and which are therefore not readily magnetized. Dependent on machining requirements, typical metals include aluminum, brass, copper, stainless steel, and others which essentially allow permeability of about 1.000. The bolt is constructed with a threaded connector. The bolt itself may vary depending on SAE standards for that particular vehicle. In some instances, metric measurements may be involved and the thread profile may be specified. Without regard to all of that, the bolt is made in accordance with these SAE standards and is the mounting device which supports the remaining two components.
The second component is a cup which serves as a holding device. The cup is attached by threading to the bolt. The cup is uniform in size and shape. The cup or holder is equipped with a drilled receptacle to receive a rare earth magnet of cylindrical form. The cylindrical shape is uniform from model to model. This reduces inventory requirements. Moreover the bolt is made of nonferrous material so that the bolt body does not spread the magnetic flux lines and thereby magnetize everything in the immediate vicinity. In effect, this creates a more concentrated magnetic field to pick up particles flowing nearby.